A nondestructive testing method using radiation has been applied to a wide range of field from an industrial application to a medical application. For example, there is an absorption contrast method using a difference in transmittance when an X-ray is transmitted through a test object. This method has been used as an application in a security field such as an internal crack inspection of an iron and steel material and a baggage inspection, using the height of the X-ray transmission capability in an absorption image obtained by the method.
Meanwhile, when the test object is made of substances having too small density difference to detect a change in contrast by X-ray absorption, X-ray phase contrast imaging for detecting a change in phase of X-rays in the test object is effective. Several of such methods have been proposed.
As one of the methods, International Publication No. WO2008/029107 discloses an imaging apparatus which provides a mask for shielding an X-ray in an edge portion of a pixel of a detector. In the absence of a test object, when setting is performed in such a manner that an X-ray is emitted to a part of the shielding mask, an X-ray positional change caused by a refraction effect of the test object can be sensed as an intensity change.
FIGS. 10A and 10B each illustrate an enlarged view of a detector portion disclosed in International Publication No. WO2008/029107. FIG. 10A is a view of the detector viewed from an X-ray incident direction, and FIG. 10B is a view of the detector viewed from a direction perpendicular to the X-ray incident direction.
A mask 1002 for shielding an X-ray is arranged in an edge portion of a pixel 1001 of the detector. An incident X-ray 1003 is incident on each pixel so as to enter a part of the mask 1002. When an X-ray is incident on a test object in such an arrangement, the position of each incident X-ray 1003 on the pixel 1001 is changed due to a refraction effect. This positional change causes the quantity of an X-ray shielded by the mask 1002 to be changed. For this reason, the refraction effect can be measured by detecting the X-ray intensity change.